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Re: [RFC PATCH 15/20] coresight: etm-perf: implementing 'setup_aux()' API

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  Re: [RFC PATCH 15/20] coresight: etm-perf: implementing 'setup_aux()' API Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-09-30 14:00 +0200
    Re: [RFC PATCH 15/20] coresight: etm-perf: implementing 'setup_aux()' API Mathieu Poirier <mathieu.poirier@linaro.org> - 2015-10-02 00:50 +0200
      Re: [RFC PATCH 15/20] coresight: etm-perf: implementing 'setup_aux()' API Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-10-02 07:00 +0200

#1236210 — Re: [RFC PATCH 15/20] coresight: etm-perf: implementing 'setup_aux()' API

Mathieu Poirier <mathieu.poirier@linaro.org> writes:

> +static void *etm_setup_aux(int cpu, void **pages,
> +			      int nr_pages, bool overwrite)
> +{
> +	struct coresight_device *csdev;
> +
> +	if (cpu == -1)
> +		cpu = smp_processor_id();
> +
> +	csdev = per_cpu(csdev_sink, cpu);
> +	if (!csdev)
> +		return NULL;
> +
> +	return sink_ops(csdev)->setup_aux(csdev, cpu, pages,
> +					  nr_pages, overwrite);

Is it guaranteed that this sink would always have .setup_aux()?

Regards,
--
Alex
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#1237807

On 30 September 2015 at 05:50, Alexander Shishkin
<alexander.shishkin@linux.intel.com> wrote:
> Mathieu Poirier <mathieu.poirier@linaro.org> writes:
>
>> +static void *etm_setup_aux(int cpu, void **pages,
>> +                           int nr_pages, bool overwrite)
>> +{
>> +     struct coresight_device *csdev;
>> +
>> +     if (cpu == -1)
>> +             cpu = smp_processor_id();
>> +
>> +     csdev = per_cpu(csdev_sink, cpu);
>> +     if (!csdev)
>> +             return NULL;
>> +
>> +     return sink_ops(csdev)->setup_aux(csdev, cpu, pages,
>> +                                       nr_pages, overwrite);
>
> Is it guaranteed that this sink would always have .setup_aux()?

A setup_aux() is vital to the design, both on Intel and ARM.  I really
don't see how one could go without it.  I can return NULL if it hasn't
been provided - that way the setup will fail without triggering a core
dump.

>
> Regards,
> --
> Alex
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#1237902

Mathieu Poirier <mathieu.poirier@linaro.org> writes:

> On 30 September 2015 at 05:50, Alexander Shishkin
> <alexander.shishkin@linux.intel.com> wrote:
>> Mathieu Poirier <mathieu.poirier@linaro.org> writes:
>>
>>> +static void *etm_setup_aux(int cpu, void **pages,
>>> +                           int nr_pages, bool overwrite)
>>> +{
>>> +     struct coresight_device *csdev;
>>> +
>>> +     if (cpu == -1)
>>> +             cpu = smp_processor_id();
>>> +
>>> +     csdev = per_cpu(csdev_sink, cpu);
>>> +     if (!csdev)
>>> +             return NULL;
>>> +
>>> +     return sink_ops(csdev)->setup_aux(csdev, cpu, pages,
>>> +                                       nr_pages, overwrite);
>>
>> Is it guaranteed that this sink would always have .setup_aux()?
>
> A setup_aux() is vital to the design, both on Intel and ARM.  I really
> don't see how one could go without it.  I can return NULL if it hasn't
> been provided - that way the setup will fail without triggering a core
> dump.

It wasn't clear to me that the sink that ends up in csdev_sink will
always be the one that does have .setup_aux(). And if it indeed doesn't,
it's better to refuse to setup a buffer than crash.

Regards,
--
Alex
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